Simultaneous determination of 38 veterinary antibiotic residues in raw milk by UPLC–MS/MS

• Thirty eight antibiotic residues were analyzed in raw milk by UPLC–MS/MS.
• Extraction procedure of antibiotic residues in raw milk was optimized.
• The proposed method achieves suitable detection limits, recoveries and precision.
• The low LOQs were fit for trace analysis of antibiotic residues in raw milk.

A selective and rapid method has been developed to determine, simultaneously, 38 veterinary antibiotic residues in raw milk by ultra-high-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). One milliliter of raw milk was diluted with 0.5 mL water and 3 mL acetonitrile, then purified using an Oasis HLB cartridge. The eluates were evaporated by nitrogen drying and then reconstituted to 4 mL with water/acetonitrile (8:1) before being injected into the UPLC–MS/MS system. The results indicated recoveries of 68–118% for 14 β-lactams, 79–118% for eight quinolones, 71–106% for eight sulfonamides, 76–116% for four tetracyclines, 78–106% for three macrolides, and 88–103% for one lincosamides, with coefficients of variation less than 15% for intraday and interday precisions. The limit of quantification for all antibiotics was 0.03–10 μg kg−1. This methodology was then applied to field-collected real raw milk samples and trace levels of four antibiotics were detected.